A new lean hybrid method based on the combination of PDCA and the DMAIC to improve process performance: Application to clothing SME DOI: 10.35530/IT.070.05.1595

ABBES NEDRA CHAABOUNI YASSINE SEJRI NÉJIB CHEIKHROUHOU MORCHED

ABSTRACT – REZUMAT

A new Lean Six Sigma hybrid method based on the combination of PDCA and the DMAIC to improve process performance: Application to clothing SME This paper proposes a new Lean Six Sigma (LSS) methodology to improve process for clothing small- and medium-sized enterprise SME. The methodology is based on combination of two approaches which are the PDCA (Plan, Do, Check, and Act) and the DMAIC (Define, Measure, Analyze, Improve, and Control). The combination technique consists in applying the PDCA to continuously improve and control every DMAIC steps. The DMAIC approach has included Lean Six Sigma tools and techniques, as well as the success factors obtained from a survey, to improve its efficiency. The proposed approach is applied to improve the performances indicators such as Z sigma, Cp, cycle time, and lead time for the case of clothing SME in Tunisia. As an example, the Z-sigma has increased from the sigma level was improved from 1.45 to 3.85. The process capability Cp from 0.5 to 1.3 and the lead time was decreased from 39.47 days to 30.23 days. Finally, the study is concluded by sorting out the effects of the type of produced articles and the presence or not of the quality certification on the application of the proposed approach. The effectives from using PDCA- DMAIC technique are better when it’s applied with certified company, than non-certified one. Keywords: Lean Six Sigma, DMAIC, PDCA, framework, clothing SMEs

O nouă metodă hibrid Lean Six Sigma bazată pe combinația PDCA și DMAIC pentru îmbunătățirea performanței proceselor: aplicabilitate în IMM-urile producătoare de îmbrăcăminte Acest studiu propune o nouă metodologie Lean Six Sigma (LSS) pentru îmbunătățirea proceselor de realizare a articolelor de îmbrăcăminte în companiile mici și mijlocii. Metodologia se bazează pe combinarea a două abordări și anume PDCA (Plan, Do, Check, Act) și DMAIC (Define, Measure, Analyze, Improve, Control). Tehnica de combinare constă în aplicarea PDCA pentru îmbunătățirea și controlul continuu ale fiecărei etape a DMAIC. Abordarea DMAIC a inclus instrumentele și tehnicile Lean Six Sigma, precum și factorii de succes, pentru îmbunătățirea eficienței acestuia. Abordarea propusă este aplicată pentru a îmbunătăți indicatorii de performanță, cum ar fi Z sigma, Cp, timpul ciclului și timpul de pregătire pentru IMM-urile producătoare de îmbrăcăminte din Tunisia. Ca exemplu, Z-sigma a crescut de la nivelul sigma, fiind îmbunătățit de la 1,45 la 3,85. Capacitatea procesului, Cp, a crescut de la 0,5 la 1,3 și timpul de pregătire a fost redus de la 39,47 zile la 30,23 zile. În cele din urmă, studiul a fost încheiat prin analiza influenţei tipului de articole produse și certificarea calităţii asupra aplicării metodei. Efectele utilizării tehnicii PDCA-DMAIC sunt mai bune atunci când se aplică la o companie certificată, decât în cazul unei companii necertificate. Cuvinte-cheie: Lean Six Sigma, DMAIC, PDCA, cadru, IMM-uri producătoare de îmbrăcăminte

INTRODUCTION commercial [15], health care [16] and logistics [17]. The Lean Six Sigma method is one famous classical The Six Sigma has two continuous models: Design approach and it’s considered among the most effec- for Six Sigma (DFSS) or Define, Measure, Analyze, tive business improvement methodology [1]. It is sim- Improve Control, (DMAIC). The second model is suit- ply a combination of the Lean and Six Sigma. Lean able for the implementation of an existing process. and Six Sigma are complementary methodology [2], According to [18], if you cannot define your process, and provide a powerful approach when combined. you cannot measure, improve and sustain the quali- Lean helps to maximize value by improving quality ty. While DMAIC is used when a product or process and reducing the source of process shift, whereas is already in existence but performing inadequately, a Six Sigma helps to reduce source of process varia- popular framework for Six Sigma implementation tion. Six Sigma reports major root causes to a prob- uses DMAIC methodology. Khaled Mili and Tarek lem [3]. It has changed over time from a metric to a Sadraoui use Six Sigma to solve the Straddle carrier business strategy [4–5], or to a strate- routing Problem [19]. Few studies have been report- gy [6–7], combined into the culture of the enterprise. ed about the application of Lean Six Sigma in small- This method is widely used in manufacturing firms in and medium-sized enterprises (SMEs) because of the world and is applied in different industrial fields, several problems [12]. A number of these have that include manufacturing [8–12], services [13–14], focused on barriers and the critical success factors industria textila˘ 447 2019, vol. 70, no. 5 in the implementation of Lean, Six Sigma, or LSS Devadasan integrate Lean Six Sigma, and ISO 9001: approaches [10, 21]. Other studies have focused on 2008 standard based System, roadmaps for implementing LSS in Textile SME. as a single framework benefiting contemporary orga- Korthi et al. were integrated model of Lean Six Sigma nization [39]. A few numbers of academic studies in and ISO 9001:2008 standard based QMS, L6QMS- manufacturing have been done on it despite the exis- 2008 model in a textile mill and thereby achieving tence of LSS for a while [36]. annual savings of 2 million INR [22]. In addition the A few Six Sigma and LSS studies of SMEs have been literature on LSS and its application in small- and done over time. The result of the pilot survey pre- medium-sized SME textile and apparel industries sented in the work of Antony 2007 in UK manufactur- businesses is limited [23]. Some authors [24] identify ing SMEs, which is primarily based on descriptive the appropriate Lean principles for implementation in statistics, shows that many of the SMEs are not textile industry. A case study is carried out in a linen aware of Six Sigma. For its successful implementa- Fabrics industry by [25] using the DMAIC methodolo- tion in SME, management involvement and participa- gy to reduce the shade variations. Lean Six Sigma tion, and linking Six Sigma to customers and to busi- application still not known and it’s limited for large ness strategy are the most critical factors for the Tunisian SMEs. Tarek Sadraoui et al., propose a new successful deployment of Six Sigma in SMEs [39]. practice of Six Sigma for reduction of the number of The result of the survey in our study in Tunisian conformities and minimization of the number of cus- Clothing SME shows that: The involvement and com- tomers’ Complaints for KITAMEUBLE industry in Tunisia [26]. The use of the complex tools remains mitment of top management Performance measure- difficult for small- and medium-sized enterprises (SME) ment and communication are the most critical factors because it requires an adapted model to success- for the successful deployment of Six Sigma in these fully implement the approach and currently faces SMEs [40]. In the same context, Taner (2012) sur- tremendous challenges and disruptive changes, trig- veyed textile SMEs in Turkey and found that lack of gered by new and capital intensive technologies [27]. knowledge about Six Sigma was the key reason why In order to ensure the improvement of projects, LSS most SMEs were not implementing Six Sigma [41]. utilizes the Define, Measure, Analyze, Improve, That’s way, the hybrid approach which is based in the Control (DMAIC) approach [28–29], integrating lean use of more than one technique have been intro- tools into a standard Six Sigma DMAIC cycle. duced to overcome the limitation of classical According to [30] and [31] the systematic implemen- approaches. As stated before, there are two different tation of this approach makes the LSS application hybrid approaches which are given in the literature. very effective. For this reasons, we can find many Combining or integration approach between PDCA, LSS implementation frameworks which are based on as most effective tool, and the DMAIC as one model DMAIC, to drive the improvements [32–33]. Vijaya of the Six Sigma, starts to be a common technique to Sunder M. presents the importance for instilling pro- improve the systems performances in the last few cess improvement culture, especially in LSS deploy- years. In the following, these approaches are ment and demonstrates how LSS project manage- reviewed and analyze. In general, we distinguish two ment can bring significant change in a retail bank main techniques. In the first one, the DMAIC is [14]. Authors such as [31–32, 9], have proposed spe- applied for each PDCA steps. We called it DMAIC- cific Six Sigma and LSS implementation frameworks, applied-to-PDCA. In the second technique, there is a based on DMAIC, to drive the improvement of spe- similar relationship between DMAIC and PDCA, in cific processes. In other studies, DMAIC approach other terms, every step in the DMAIC find an equiva- has been applied, with specific tools in every stage lent in PDCA steps; we called it DMAIC-similar-to- [34–35, 9]. Tools such as Value Steam Mapping, Total PDCA. Productive Maintenance (TPM), DoE, SPC, and The principal of the first technique consists in apply- QFD are still a key to LSS implementation success ing the DMAIC technique to the PDCA cycle. Every [36]. single steps of the PDCA is subjected to be controlled Some authors [37] proposes a new LSS Framework by all over the DMAIC cycle in order to improve the based on the integration of the DMAIC cycle at each point in the Lean thinking cycle. One issue of this standard implementation, as well as the process [42]. method is that the predominance given to the Six The second technique is based on the similarity in Sigma DMAIC cycle within the existing LSS frame- the principals of PDCA and the DMAIC. In other work can make Lean viewed and utilized as a tool kit terms, there is equivalence between every singles of techniques, and removes the opportunity to use steps or more from the DMAIC and the PDCA steps. Lean as a strategic thinking approach within the LSS For example the equivalent of Plan is Define; the framework. This can drive quality-based improve- equivalent of Do is Measure... In this approach, the ment projects rather than Lean-based projects or PDCA is the main player that influences the perfor- projects that create a dual impact of both quality and mance of the DMAIC and not the opposite as in the efficiency improvement. Everton et al. identify and first one. The advantage of this approach is to relate analyze the difference and the complementariness in Six Sigma initiative to PDCA cycle in order to ensure the production areas for three models, Lean Six the comprehensive micro and macro within an orga- Sigma and Lean Six Sigma [38]. S. Karthi and S.R. nization [43]. industria textila˘ 448 2019, vol. 70, no. 5 Although that these hybrid methods bring some PDCA cycle because it adds the rigor of project life- advanced comparing to the classical ones, they still cycle (PLC) to the implementation and close-out of present some limitations and drawbacks which are: Lean Six Sigma projects. Every approach, which is • Even that the first approach to be effective accord- being introduced into an organization, can be checked ing to his others, its principal seems to be not logic against the PDCA cycle, as follows: The ‘Plan’ phase and reasonable. This is because the PDCA by its allows verifying that applied approaches are well nature as a helpful procedure could not be subject- integrated and focused on the all needs. The ‘Do’ ed to the DMAIC approach, but the opposite. In fact phase aims to check the systematic implementation it’s the PDCA which should be used to improve the of these approaches and the existence of appropriate DMAIC. Every approach, which is being introduced measurement tools. In the ‘Check’ and ‘Act’ phases, into an organization, can be checked against the we can check that these approaches are measured PDCA cycle, which proves our idea. and improved. While Lean six sigma projects in com- • The second limitation is that the given study pre- panies can be adhered to a system that ensures con- sents lack of implementation in real word applica- tinuous improvement such as PDCA. We believe tions, which reduce the effectiveness of the pre- framing Six Sigma projects within a PDCA cycle pro- sented methods. vides a more comprehensive view of Six Sigma • In the second approach, we think that improving implementation in clothing SMEs. In this section, the one or more steps of the DMAIC using only one developed methodology, to come out with a LSS step of the PDCA is not sufficient to improve all the model in order to improve the quality and the produc- process. This because every DMAIC step can be tion in clothing SME, is presented. This model is seen as a complete process from the side of the applied for the case study of tow clothing SMEs to: PDCA. (1) Achieve a higher quality; (2) Increase process The main contributions of this work are: speed; (3) Reduce waste and (4) Increase Customer • To develop a novel methodology based on the inte- satisfaction. Every step is detailed below. gration of two approaches PDCA and DMAIC, in order to improve the system efficiency and ensure the continuous improvements. • To review and analyze the existing approaches used in process improvements systems. • To apply the developed approach on one certified Tunisian clothing SME producing technical articles and compare the obtained results with other non- certified one producing Denim articles.

MATERIAL AND METHOD This article presents a study on deployment of LSS framework in Tunisian clothing SME. The developed framework is based on the integration between DMAIC approach and PDCA cycle. The framework incorporates the tools, techniques and the critical success factors (CSFs) of LSS application, which are determined by a survey in a sample of well studies clothing SMEs, to be applied for each DMAIC steps. We think that a new methodology has to be intro- duced in order to solve the discussed issues. This Fig. 1. PDCA-applied-to-DMAIC methodology is basically the opposite of the DMAIC- applied-to-PDCA because it’s more effective that every step to be subjected to all the PDAC cycle. The RESULTS principal of the proposed approach is basically the Modeling a LSS methodology opposite of the DMAIC-applied-to- PDCA, so that, we The developed model uses the technique of integra- called it PDCA-applied-to-DMAIC. The principal is tion between DMAIC approach and PDCA cycle. In described by figure 1. The established framework our work, we have chosen to apply the PDCA cycle PDCA is applied to each DMAIC steps to improve to every single step of DMAIC (figure 2). This can continuously the process, focusing on continuous improve every sub-system performance and there- learning and knowledge creation. The PDCA (Plan- fore, it can guarantee the success of the complete Do-Check-Act), cycle is the basic procedure of TQM. process. This procedure is applied to all the DMAIC It is more than quality tool but also is a fundamental steps, but in our paper we limit to give explanation of approach of continuous improvement. In fact, it was Define step. The details of DMAIC structure are given considered as a well-established framework for pro- in figure. As it can be seen, the tools and techniques cess improvement where it focuses on continuous have been integrated into the corresponding DMAIC learning and knowledge creation. We choice the step. We mentioned that the modeling of the DMAIC industria textila˘ 449 2019, vol. 70, no. 5 the importance of and the need for the Lean Six Sigma project and its deliverables. A project schedule SIPOC (Supplier Input Process Output Customer) diagram for the entire loading opera- tion was created in order to provide a clear picture on the suppliers, customers, needed input materials and the sequence of processes involved in manufacturing the product (figure 3).  The Measure phase: In this step, data on measur- able indicators of production processes are collected. The objective is to deter- mine the sigma of the pro- cess which in turn can give Fig. 2. Modeling a LSS methodology DMAIC steps us an idea about the pro- cess capability index and approach was carried out using the BPMN standard, because it can give an easy and clear picture of rela- tionship between DMAIC steps. PDCA Cycle for Define Plan: The objective of the Plan step is to reach the cus- tomer satisfaction which represents the main out- put of Define-step, and to develop its necessary sub-stages. Do: The Do step consists in the real implementation of the Plan step. Check: In the check step, the customer satisfactions are continuously evaluated, also the success key fac- Fig. 3. High level SIPOC diagram of the case study tors are controlled to prevent any problems and to guarantee the success of Define step. Act: hence its performances and Identify the types of In case there is a lack in the required outputs, or waste generated by the studied processes. any undesirable results, the Act step is applied to Process capability Measure fix the problem and to improve the process perfor- The analysis of capability is performed to find out mances. actual state of the process]. Once the data are calcu- lated, two sub-processes capability studies are con- Case study ducted: production and cutting. The study was conducted in a small clothing compa- The variation for both processes (production and cut- ny specialized in the manufacturing of automotive ting) capability is shown in figures 4 and 5. articles located in Tunisia. The firm is certified with From these figures, we conclude that both processes ISO 9001. It interested in improving its sigma level are incapable, because the Cp is lower than 1.33. and the customer value. The Z of the complete process is equal to 1.45.  The Define phase: Process modeling and Simulation The initial step in the Define phase consists in form- We propose to show the interest of using the simula- ing the team. The project team should be composed tion not only to validate the modeling of the process by with employees, who are responsible for perform- but also to define and position the data acquired to ing the ship loading process. As management com- calculate the performance indicators and to test the mitment is the most important key of LSS implemen- proposed improvements before implementing them tation success. A meeting was prepared by the top on the actual process of a clothing SME. This model- management in order to explain the employees about ing and simulation will be done with BPMN standard industria textila˘ 450 2019, vol. 70, no. 5  Analysis phase: The analysis phase examines the collected data in order to generate a prioritized list of source of varia- tion in order to identify the root cause and to analyze the problems of process inefficiencies, using the result of the step “Measure”. The used tools in our work are the following: • Identification of failure modes and their causes Based on the available data, the main rejection defects of the product were identified. Seven failure modes that led to the rejection were identified. Table 2 shows the main rejection and their category Fig. 4. Process capability of cut sub-process report for the net. before improvements implementation Table 2

MAIN REJECTION AND ITS CATEGORY

Defect Category of defect The net is assembled in the Security defect wrong position Incorrect net height Security defect Incorrect total length Security defect Low resistance of keder Security defect Discontinuous stitching Customer satisfaction Incorrect position of loop Customer satisfaction Incorrect keder length Security defect Fig. 5. Process capability of production sub-process report before improvements implementation All these defects have effects on user safety, cus- using the tool BiZagi (figure 6). Table 1 summarizes tomer satisfaction, or on the installation of the article the evaluation of performance indicator. in the truck. In fact during an accident, the net does not perform its main function of preventing the user Table 1 from moving forward. • Root cause analysis EVALUATION OF PERFORMANCE INDICATOR The cause and effect diagram (as shown in figure 7) was drawn to find out the causes of “security defect”. Indicator Values Sub-causes were categorized into five general cause Cycle time 9 h 15 min categories namely Material, Personnel, Milieu, Methods and Machines. Total average waiting time 8 hour 35 minute 23 s Cause and effect diagram shows that the most impor- Value added time 24 min 25 s tant causes that affect the defect are essentially due • Post prepare piece: 98,9% Resource utilization to: operator error, bad machine setting, lack of mate- • Post Mount piece: 41,2% rial control at reception, or lack of worker training. We analyzed all other types of defect using the cause-effect diagram  Improve Phase We have concretized the planed actions, respect the deadlines. Since the training and education is among the key factors of success of LSS application, training to the employees involved in implementation of the improvement activities are provided in order to assure the successful implementa- tion. Tools and techniques Fig. 6. BPMN diagram model of the sub-processes 5S, , Poke yoke and industria textila˘ 451 2019, vol. 70, no. 5 Production System (TPS). The kaizen activities were proposed to improvise activity that does not create any value. The kaizen activities were planned such that the overall performance gets improved. Creation of a facility layout We have organized separate standalone workflows after applying operator training to different operations performing in the same cell. The process flow allowed us to identify a waste in terms of transport. In order to optimize the movement between the work- Fig. 7. Cause and effect diagram stations and the storage areas of raw materials and accessory, we implemented storage area in the work- other process improvement techniques are applied flow. Figures 8 and 9 show the existing layout and the for planning the improvement activities related to modified layout. quality and productivity. To validate the obtained results of the improve phase, a confirmatory test was implemented by measuring again process capability and performance indicators.

Table 3

PROPOSED SOLUTION FOR REJECTION DEFECT

Defect Proposed solution The net is assembled Construction of a table by in the wrong position serving Poke yoke Low resistance of Request to do tests in the keder laboratory Discontinuous Fixing number of pieces per stitching bobbin Incorrect position of Placing two markings on the loop table for the loop position Fig. 8. Existing layout Cut the keder in the workshop Use the lime cutter fixed on the Incorrect keder length table Place a mark on the cutting table

Table 4

CORRECTIVE ACTIONS FOR EXISTING MUDA TYPE

MUDA type Corrective actions Excessive Minimize the displacement by creating displacement a storage area in the chain Excessive Minimize the quantity manufactured storage per lot Unnecessary Eliminate intermediate control, Study operations and develop key workplace

Table 3 and 4 show the improvement activities pro- Fig. 9. Modified layout posed by the team members. Appropriate solutions were provided for each defect and were implemented. 5S Validation of best solutions Before the application of the improvement project In order to validate the obtained results of the using the 5S method, the key factors of success in improve phase, a confirmatory tests were conducted order to successfully implement the 5S are fixed. to validate the modifications. Results showed that To reduce the non-value added time for employees, after implementing the improvement actions, varia- the team starts working on the pillars constituting the tion has been decreased consistently and the pro- 5S method. cess is properly centered. Sample of 30 components Implementation of process Kaizen were taken and were measured in two sub-process- Kaizen Continuous improvement (kaizen) is one of es to find its process capability. The process is shift- the principle concepts that support the Toyota ed towards the center mean and it is capable of industria textila˘ 452 2019, vol. 70, no. 5 Fig. 10. Process capability of sub-process production Fig. 11. Process capability of sub-process cut report report after implementation after implementation

Table 5

PROCESS PERFORMANCE INDICATORS BEFORE IMPROVEMENTS Sub-pro- Process Z Cp Z BPMO cess capability process

Cut 1.3 3.89 Capable a 10700 3.89 Production 1.36 4.07 Capable producing the components with the specification lim- its. The obtained process capability for two sub-pro- cesses after implementing the improvement actions is shown in figure 10 and figure 11. Table 5 presents b the significant improvements after implementation of Fig. 12. Control chart of process for (a) sub-process cut Lean Six Sigma methodology of processes. and (b) sub-process production  Control phase The applied improvements have been fully integrated implementing the Lean Six Sigma framework includ- into the training regime and the process documenta- ed Z-Sigma, Process Capability Cp, Defects per mil- tion, the information related to company performance lion opportunities (DPMO), Cycle time and Lead time. was sharing with its employees. A regular audit of The main conclusion that can be summarized from parameters setting was carried out. Visual manage- the obtained results and indicators shown in table ment, Total Productive Maintenance and Process are: FMEA are to be implemented after completion of the • The effectives from using PDCA-DMAIC technique project to provide a visual aid for controlling the key are better when it’s applied with certified company, input and output variables pertaining, and to ensure than non-certified one. This is because they already the team could not revert back to old habits. The con- applied standards tools of the ISO 9001 witch can trol charts are a powerful tool for achieving process help to better use of Lean Six control and stability. For this project, the implementa- • The type of produced article has also a consider- tion of control charts was important to check that the able effect on the success or not of Lean Six Sigma product meet the desired specifications. Figure 12 application, for example security articles recom- shows the control charts for the sub-process cut and mend some obligation to reduce at a minimum the sub-process production respectively. We can show safety defects. the process in general, is in control and stable. • The increase of Z in SME specialized in denim arti-  Evaluation of the PDCA-applied-on-DMAIC cles are not of ease and achievable task because The DMAIC approach which is applied in certified the probability of defects is high. company is again applied with a non-certified one dif- ferent in specialization to investigate its effects on the DISCUSSION performance of both companies. Table 6 shows the On completion of this project, we have first conclud- results after improvements of two companies: The ed that the existing approaches have several limita- key metrics used for comparing the results after tions and issues, these limitations can be due to a industria textila˘ 453 2019, vol. 70, no. 5 Table 6

RESULTS BEFORE AND AFTER IMPROVEMENTS OF TWO COMPANIES

Technical articles (Certified ISO 9001) Denim articles (Not Certified ISO 9001) Key metrics used Before improvements After improvements Before improvements After improvements Z-Sigma 1.45 3.85 0.7 1.2 Cp 0.5 1.3 0.2 0.7 DPMO 540000 10700 780000 308000 Cycle time 19.92 min 14.54 min 12.79 min 10.1 Lead Time 39.47 day 30.23 day day 13 day lack in a good comprehension on how to apply the mances indicators such as Z sigma, Cp, cycle time, hybrid techniques such as the case of DMAIC- and lead time for the case of clothing SME in Tunisia. applied-to-PDCA. In addition to that, these approach- The methodology is based on combination of two es don’t find a real application in our real word which approaches which are the PDCA (Plan, Do, Check, limits its use and the reliability of the given results. On and Act) and the DMAIC (Define, Measure, Analyze, the other side, the new proposed approach has bet- ter fundamental basis as it uses the PDCA, which is Improve, and Control). Finally, the study is concluded one of the most effective tool, to continuously improve by sorting out the effects of the type of produced arti- and control the DMAIC process. In contrast to the cles and the presence or not of the quality certifica- existing approaches which have a lack of real appli- tion on the application of the proposed approach. cation, we have applied this proposed approach to In our case study, as with our recent work [40], clothing certified SME. The approach also integrate Management commitment and involvement was the Lean Six Sigma tools and techniques like Kaizen, most important Critical success factors and the Pokayoke, Pareto..., and the key factors for LSS suc- Acceptance of Lean Six Sigma Culture was the most cess. These tools were determined from survey achieved in a Tunisian clothing sample SMEs and important indicator for implementation of LSS in used in every DMAIC step. clothing SME. Although initially, the employees of the The results prove that the proposed approach can be studied case believed that the implementation of LSS used as an effective and efficient tool to improve pro- could affect their performance change their working cess performance. As an example the sigma level practices, and eventually endanger their job opportu- was improved from 1.45 to 3.85. Improvements were nities. Other major issue was only basic lean tools observed from l lean metrics such as cycle time and lead time. and techniques had previously been employed (5S, Furthermore, the proposed was applied in other non- etc.) because of the lack of knowledge about Lean certified SME producing denim article to investigate Sigma tools by the employees. the effect of whether the company is certified and the The proposed LSS framework has been test imple- effect of the produced articles on the rate of success mented in two Tunisian Textile SMEs, one is certified of LSS implementation. It was shown that the effec- producing technical article and one non-certified pro- tives from using PDCA-DMAIC technique are better ducing denim article, and focused on addressing one when it’s applied with certified company, than non- specific problem (i.e. defect). In the future, this frame- certified one and the type of produced article has also a considerable effect on the success or not of Lean work can be used as a base and adapted to drive Six Sigma application, for example security articles improvements in other textile SMEs and to hold other recommend some obligation to reduce at a minimum operational problems. In addition, more tools and the safety defects. techniques can be added, or removed, from the framework for specific adaptation and improvement. CONCLUSIONS, LIMITATIONS AND FUTURE RESEARCH DIRECTIONS ACKNOWLEDGEMENTS This study aims to propose a new Lean Six Sigma We would like to thank the director of the company in which (LSS) methodology to improve the process perfor- we applied our work.

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Authors: ABBES NEDRA, SEJRI NÉJIB, CHAABOUNI YASSINE, CHEIKHROUHOU MORCHED Textile Engineering Laboratory (LGTEX), Higher Institute of Technical Studies of ksarhellal (ISET), Monastir University, Tunisia

Corresponding author: ABBES NEDRA e-mail: [email protected]

industria textila˘ 456 2019, vol. 70, no. 5